Re: Does water (fresh or salt) affect the power of magnets?

Dear Steve!

In principle, the answer to your question is yes. Water is (like most `common' materials) diamagnetic, i.e. it has the property to expel (to some extent) magnetic fields. If you put some water near a magnet, the water molecules arrange in such a way that the field emerging from the magnet gets attenuated -- the field lines tend to take a `detour' around the water. This has nothing to do with the fact that water is (more or less) a conductor.

Putting a magnet under water has thus the effect of weakening its magnetic field, it gets `screened'. Nevertheless, this effect is very weak and I am not sure whether it is measurable using `normal' magnets. You might be able to see a small effect using Neodymium-Boron magnets (very strong permanent magnets). Under no circumstances will `power' be `drained' from a suspended magnet permanently. Taking the magnet out of the water will restore its strength.

There is another, very spectacular experiment which shows the diamagnetism of water. Take a plate and fill some water into it. Holding an NB magnet right above the water surface, you might notice a very slight deformation -- the water tries to `escape' from the strong magnetic field. This is called the `Moses effect', for obviuos reasons. Other impressive experiments have been performed using the diamagnetism of natural materials.

Hope that helps,
Georg.